Support base



FIG. 1 is a perspective view of a support base;

FIG. 2 is a top plan view, the bottom plan view being a mirror image;

FIG. 3 is a rear elevation view;

FIG. 4 is a side elevation view, the opposite side being a mirror image;and,

FIG. 5 is a front elevation view.

The broken lines are for environmental purposes only and form no part ofthe claimed design.

The ornamental design for a support base, as shown and described.